This article is complementary to Barrie Russell’ s excellent article and“ Mustang” plan that will be available via our website in the near future. Barrie and I have done some soul-searching over this and agree that while it may be teaching some of you how to suck eggs, there’ s always a steady stream of new chums who have not yet discovered the joys of fabricating with foam. This will be a series over the next few issues.
Firstly, there are only a few books on foam-cutting, but a ton of articles on the Internet. A couple of good books are:“ Radio Control Foam Modelling” by David Thomas and“ Building with Foam” by Keith Sparks. The Thomas book is more comprehensive and if I had to choose just one, then the Thomas book would be it.
But, please, if you are using a power supply other than an off-the-shelf power supply that is intended for foam cutting, GET YOURSELF AN RCD BEFORE ANYTHING ELSE!! It’ s the cheapest insurance you will ever buy, and it can save you from your own carelessness, or not thinking for 0.1 second, as that’ s all it takes to be electrocuted. Mitre 10 has the“ Buyright” one for $ 13.24 and one other brand for about $ 16; Bunnings has one for about $ 15 and while I have not checked, I’ m pretty sure that Placemakers will have one too.
Righto, here we go: I recently had a need( see Barrie Russell’ s Mustang plan) to cut a sheet that tapers from 25 mm thick at one end to a mere 5mm at the other. Picture 1 shows the easy way to do this. Set up a hot wire above the bench with a 25mm tube at one end, and a 5mm drill at the other. Then just feed the foam underneath it like a woodworking thicknesser. Note that you don’ t need to power up the whole length of wire, just the section that is doing the cutting.
Obviously, if you require a parallel sheet, just place the correct( and same) sized spacer under each end
Then, the next task is to cut out the fuselage profile, What you need is a“ foam jigsaw” and one is easily made, just rig up the wire vertically, Picture 2 shows my setup. The lower end is locked into a plug in the bench, while the upper end is spring loaded to a ceiling hook. Once again, you only need to heat the part that does the cutting, note the red and black alligator clips attached where it matters.
To cut out channels for servo wires etc, a small shaped cutter is required. Picture 3 shows two of these. The wire is 16 awg Nichrome but stainless steel might work as well. The dowel handle is essential, not only to hold and guide the cutter, but also be aware that things( including the leads) get pretty warm.
Barrie Russell has covered normal bows quite well, but I find a small short bow quite convenient from time to time. Picture 4 shows one I converted from an old hand fretsaw. Note the nylon bush at one end to avoid shorting out the wire. Picture 5 shows the method I use for terminating and tensioning a normal 1 metre bow. I use. 020” Inconel lockwire, but Nichrome works, as does thinner MIG welding wire, or stainless steel if you can find it.
Then to cut out tapered wing panels. I used to do this with two templates and a“ helper” trying to keep track at some roughly similar rate. Warning, if you use your wife / partner / SO for this, it has been reported that disharmony can result! Sometimes it works out well, other times less so..
Then a number of years ago, I stumbled across an article in“ Model Builder” that was an epiphany.